Vehicle fuel systems include evaporative emission control systems designed to reduce the release of fuel vapors to the atmosphere. For example, vaporized hydrocarbons (HCs) from a fuel tank may be stored in a fuel vapor canister packed with an adsorbent which adsorbs and stores the vapors. At a later time, when the engine is in operation, the evaporative emission control system allows the vapors to be purged into the engine intake manifold for use as fuel.
Diverting fuel vapor located in the fuel tank to the fuel vapor canister prior to refueling is especially important for hybrid electric vehicles (HEVs). Such vehicles are designed to run primarily on an electric motor and only occasionally use the internal combustion engine, resulting in fewer opportunities to purge the fuel vapor canister. Furthermore, HEVs feature a fuel tank isolation valve that seals the fuel tank to maintain fuel vapor within the tank during vehicle operations. Without regular purging of the evaporative emission system, normal vaporization of the liquid fuel in the tank will cause the tank to become pressurized above atmospheric pressure. Prior to a refueling event, fuel tank vapor needs to be vented to the fuel vapor canister to prevent evaporative emissions via the fuel filler neck. Further, an over-pressurized tank (e.g., fuel tank pressure greater than ambient pressure) may result in liquid fuel splashing out of the tank when opened.
To lower the fuel tank pressure to atmospheric pressure prior to refueling and therefore prevent fuel vapors from escaping into the atmosphere, HEVs come equipped with a dashboard-mounted refuel request button that a driver presses prior to refueling. Requesting a refueling event triggers a controller to open the fuel tank isolation valve, depressurizing the fuel tank prior to allowing access to the fuel filler neck. However, the location of these refuel request buttons on the dashboard is unintuitive and inconvenient. If a driver forgets to press the button prior to exiting the vehicle at the refueling station, he or she must re-enter the vehicle in order to prepare the vehicle for refueling. Further, a refueling operator approaching the refueling door from the outside of the vehicle has no control over the tank depressurization process. Additionally or alternatively, after depressing the button, there is no visual indication to the driver that the fuel tank is being depressurized, which may result in excessive depressions of the button.
The inventors herein have recognized the above described problems, and have developed systems and methods to at least partially address these issues. In one example, the issues described above may be addressed by a method comprising gradually opening a refueling door in proportion to a fuel tank depressurization rate via an amount of current supplied to an electrorheological fluid located in a locking mechanism of the refueling door. In this way, the refueling door gradually opens as the fuel tank is depressurized, providing a visual indication to a driver or fuel attendant that the refueling request is received.
As one example, after depressing a fuel tank fill-up request button, which may be a dashboard-mounted or externally-mounted button, current flows to the electrorheological fluid to maintain the refueling door closed. The fuel tank is depressurized and the rate of depressurization is estimated. The current to the electrorheological fluid is decreased and the refueling door is incrementally opened as a force of a spring overcomes the viscosity of the electrorheological fluid. In one example, the current is proportional to the depressurization rate such that the refueling door is fully open once the fuel tank is sufficiently pressurized. By doing this, the refueling door is moved to a fully open position when the fuel tank pressure is substantially equal to atmospheric pressure. As such, the refueling door gradually opening provides a visual indication of receipt of the refueling request and a duration of time needed to depressurize the fuel tank to atmospheric pressure.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.